Electrical connector



' Aug. 28, 1951 l. w. EDWARDS 2,565,652

ELECTRICAL CONNECTOR Filed Aug. 30, 1947 3 Sheets-Sheet 1 INVENTOR.

Irving WEdwards ATTORNEYS 1951 1. w. EDWARDS 2,565,652

ELECTRICAL CONNECTOR 3 Sheets-Sheet Filed Aug. 50, 1947 IN V EN TOR. Irving WEdWards BY vQ L ATTORNEYS IN V EN TOR. [rvz' 129 74/1? dwa rds BY Patented Aug. 28, 1951 UNITED STATES ATENT OFFICE ELECTRICAL CONNECTOR Irving W. Edwards, Detroit, Mich.

Application August 30,1947, Serial No. 771,525 8 Claims, (01. 287-203) This invention relates to electrical connecting conductors, and more particularly to conductors of the type commonly known as jumpers or ground straps used for establishing electrical continuity.

The principal object of my invention is to provide an electrical connection or bond of this type which may easily be applied by work-men in the art and which provides a good electrical connection which is maintained secure in spite of shocks and vibrations or other factors which tend to loosen or impair the connection.

This is a continuation in part of my copending application, Serial No. 605,319, filed July 16, 1945.

My connectors are particularly applicable as railbonds and may also be used to establish electrical connections to such structures as steel shapes, bus bars and pipe lines.

In railway track circuit signalling which is an important field of use of my connector or bond, it is the practice electrically to connect each rail to the next by an electrical conductor or railbond of low enough resistance efiiciently to conduct the relatively small signal currents along the rails. The bond ordinarily comprises a flexible electrical conductor long enough to extend from a point near the butt end of one rail to a similar point near the butt end of the next, with sufiicient slack to allow for vibration and expansion and contraction of the rails and for play in worn bolts and bolt holes. Each end of this flexible cable is securely attached to and terminated by a stud adapted to be fitted into a hole bored in the rail head, or the web of the rail.

Various means have heretofore been proposed for effecting a good electrical connection between the stud and the rail and for holding the stud securely in the bore to maintain the connection. According to one such proposal, a bore is formed centrally within the stud, and a pin is placed in this stud bore, after which the stud is hammered into the bore of the rail head, thereby wedging the pin in the stud bore to expand the stud against the rail bore and hold the connector in place.

I have found that such prior known connectors, while many times giving good service, frequently cause trouble, sometimes because of imperfect electrical connection or breaking of the stud and sometimes because the stud can be vibrated out of the hole.

In accordance with the disclosure of my said copending application, I have overcome the undesirable feature of the prior known connector studs by the use of a centering ball.

By reason of the proportioning of the parts so that the ball located in the recess of the stud projects somewhat beyond the end of the stud, provision is made for the ball to center itself at the cupped base of the bore in the rail head, thereby bringing the stud to a centered position. Because of this centering feature, the stud can be driven home by hammer blows without undesired cocking or offsetting and a, secure sealing against moisture and locking of the stud in the bore is provided with attendant good electrical connection. This sealing and locking of the stud in the bore occurs primarily at the region near the outer end of the stud, resulting in the eificient type of locking had by use of my connector, with little or no tendency of the stud to shear or break off at the base.

By appropriately shaping the stud recess, I am enabled by the use of the ball, to adapt the connector to many kinds of applications, both as railbonds and as connectors for other purposes.

I have discovered in accordance with my present invention that the centering member need not be exactly spherical as specificall disclosed in my said copending application, but instead, may be varied somewhat from the exact ball or spherical shape. For example, it may be made in the shape of a spheroid or an ovoid. By a spheroid, I mean a shape which is not quite spherical, for example, it may be a flattened or lengthened or somewhat distorted sphere. A shape which it may have, for example, may be that of an ovoid, by which I mean a shape which is partly spherical at each end, and the diameters of the two partial spheres need not be the same. Other similar shapes may be employed, for example, truncated spheroids or ovoids and the like. Generally these spherical, spheroidal, ovoidal, etc., inserts may be classed as bodies of such shape that any section therethrough will define an area at least partly bounded by curved lines. Thus cones, cylinders and the like are not included within the generic definitions for a vertical section of a cone or cylinder is bounded by straight lines, i. e. a triangle or a rectangle. In any event regardless of the particular variance of the shape which may be employed, the centering device is placed in the central recess of the stud, as explained in my said copending application, so that when the head of the stud is hammered into the bore of the rail, there Will be a binding action of the stud Within the rail. By suitable selection of the various shapes of spheroid or ovoid and the like from which selection may be made, it is possible to apply to the stud different variations and distributions of binding 3 force, as will more particularly appear hereinafter.

The foregoing and other features of my inven tion will be better understood from the followin detailed description taken in conjunction with the accompanying drawings of which:

Fig. l is a partial view, in horizontal crosssection taken at line 1-4 of Figs. 2 and 4, through the rail heads of a pair of abutting rails, showing the rails connected by a railbond according to my invention;

Fig. 2 is a partial vertical cross-section view through a rail head, taken at line 2-2 of Fig. 1, showing the connecting stud and its cable;

Fig. 3 is a front elevation view of the railbond shown in Fig. 1;

Fig. 4 is a vertical cross-section view showing part of a rail, the cross-section being taken through a stud. hole in the rail head, for example at line 44 of Fig. 1;

Fig. 5 is an enlarged partial view partially in cross-section, taken at the same horizontal section as Fig. l, and showing in detail the construction of the stud with its recess and ball;

Fig. 511. show graphically the pressure distribution of one of the driven studs of my invention;

Fig. 6 is a side view of the stud of Fig. 5, made according to my invention, the cable wires being shown in cross-section;

Fig. '7 is a top view of the railbond made according to my invention, showing the conn cting cable arranged in a serpentine manner;

Fig. 8 is an enlarged view of an undriven railbond according to my invention, showing the attaching stud welded to sleeves which enclose the cable;

Fig. 9 is a view partially in cross-section showing a short connecting stud according to my invention adapted for connection with a metallic member or the like, and showing a multiple cable entry into the sleeving attached to the stud;

Fig. 10 is a plan view of one arrangement of the cables of the railbond;

Fig. 11 is a side elevation of the arrangement of Fig. 10;

Fig. 12 is an end elevation of the arrangement shown in Figs. 10 and 11, the rail and splice bar being shown in section;

Fig. 13 is a section taken on the line Ill-13 of Fig. 11, and Fig. 13a illustrates the pressure relationships as the stud is driven into the rail;

Fig. 14 shows a composite wedge-tapered insert with rounded ends and tapered recess;

Fig. 14a illustrates the pressure relationships obtained with such a combination;

Fig. 15 shows a modified ovoid centering insert;

Fig. 16 shows yet another modified insert;

Fig. 17 shows a stud provided with an ovoid recess to accommodate an ovoid insert;

Fig. 18 shows a modified form of the shape shown in Fig. 17;

Fig. 19 shows a modified recess and insert; and

Fig. 20 shows a modified insert in a standard recess or bore.

In Fig. 1 there are shown the abutting ends of the heads of adjacent rails H and I2 in a railroad track, the ends of the rails having the usual clearance between them. In the figure, the rails are shown in a horizontal cross-section taken at line I-l of Fig. 2 and of Fig. 4. Fig. 2 shows a vertical cross-section through rail II, the top of the rail on which the wheel rolls being indicated as [3. Fig. 4 shows a vertical section through rail [2, the top of the rail being marked [4. In each of Figs. 1, 2 and 4, only a portion of the section through the rails is shown, enough to illustrate the application of my invention.

For the purpose of applying my connector to the rails, I provide a bore in the side of the rail head near the abutting end of each rail, the bore in rail H being numbered l5 and the bore in rail !2 being numbered l6. Each bore is of a cylindrical shape such as may be made by an ordinary drill. and the end of each bore is brought to somewhat of a point or apex which may be, for example, cone-shaped, as shown at in Fig. 4. This shape need not necessarily be exactly conical, nor brought to a definite point, but should be cupped somewhat similar to a cone, so that a ball may readily set itself therein in one definite position or orientation. This shape of the base or termination of the bore, I call herein cupshaped regardless of whether it is exactly conical or somewhat curved or rounded.

For the purpose of electrically connecting the abutting rails, I provide a connector ll according to my invention (Fig. 3). The connector, or railbond l1 comprises an electrical conducting cable, or preferably a plurality of parallel cables [8, terminated at their respective ends in terminal members 59 and lea. The arrangement used for fastening the cable to the terminal members is a system of concentric sleeves 2i] and 2|, welded to terminal !9, and sleeves 20a and 2m welded to terminal l9a. To make connection, the heads 22 and 22a may be concaved to some extent at their ends next to the cable; and the outer sleeve 2! with the inner sleeve 20 firmly telescoped in it, is then welded at 23 (Fig. 5); Similar construction is used at the other end of the cable at 2011, 2m, 2211 and 23a. The cable wires themselves may be attached within the inner sleeve by any suitable means such as swaging, soldering or welding, or any or all. The inner surface of each terminal member i9, adapted to be placed parallel with the side of the rail head, is preferably made flat at 24 (Fig. 5). A stud 25 protrudes perpendicularly from the flat inner surface, and the stud is of a size and shape to fit snugly in the bores i5 and it in the rail head. Preferably the stud is bevelled somewhat around the circumference at its forward end as shown at 50, (Fig. 6) to facilitate starting it in the bore.

A recess 26 is provided centrally within the end of each stud. The recess is so shaped that its widest dimension or diameter is near the end of the stud at a position 2'!, and narrows down toward the base 28 of the recess. The recess is purposely so shaped that its successive cross-sec tions in going from the outer end of the stud toward the base 23 are circles of decreasing diameter. This shape of the recess enables a ball 39 to be placed in the recess far enough so that the maximum diameter of the ball goes down past the edge of the recess at 3!. The ball can accordingly be held against falling out of the recess by crimping in the leading edge 3| of the stud around the ball, as shown in Fig. 5, while still allowing somewhat less than a hemisphere of the ball to protrude beyond the stud at 32. The ball is preferably of a very hard non-deformable material, such as a hardened steel ball-bearing, and its surface is preferably provided with a good smooth finish or polish. The material of the stud is likewise a metal or a resilient conducting solid or plastic but not as hard as the ball. It may be made of a somewhat softer but elastic steel or of bronze or the like, which will conduct electricity and will compress when forced by the accepts relatively hard ball. andflow around. and. expand after passa e. of the ball.v This. deformation and flow oi the stud. is a. featurev common to. this. and to. the other: modifications hereinafter described.

To. establish a connection by the use of my conhector, the stud isv inserted into the bore and then driven by a suitable driving, hammering or compressing operation. If-the outer edge of the stud is, tapered, as. describedpabove, the stud: can easily bev started, and. can havea, shape to conform with the cupped bottom "in of the bore. As th stud is. pushed into the bore, itshould' preferably fit, snugly, although it can bewell iastened into. thev borev even though the ,bore be. somewhat oversize. The forward part of theball should be set againstthe inner conical or cupped part of they bore. at the circle of contact marked 3,3 in Fig. 5, which will serve to center the ball and stud even though there maybe some other slight misalignment between the studand the bore. The stud should be proportioned so that when the ball strikes the conical 'or cupped portion of the bore, the forward annular. edge M of the stud should remain separated. at some distance from the end I Ba'of the bore as shown in Fig. 5.

For the purpose of the driving, it will be convenient in diflicult locations to apply a pressure tool or a driving punch to the recessed head 220! (Fig, 5) of the stud, and then hammer on the punch, though this can usually be done directly on the terminal by a hammer. Upon. thecommencement of the. hammering, the driving of the stud forward against the maximum diameter of the ball will serve to expand the stud outwardly to. a, larger diameter near its forward end at about th position of maximum diameter of the ball, thereby locking the stud to the rail near the forward end of the stud. This initial locking serves as a backing; against which the stud is further upset progressively, upon further driving, so that the locking area progresses from near the tip. end of the stud toward the base of the stud. This upsetting and locking will continue progressively as the stud is driven so that the ball is forced farther and farther inward into the recess of continually diminishing crosssections.

As rough approximation, the-area of greatest pressure tending to bind the stud into the bore exists from the region of about point 34 to point 35 (Fig. 5a) around the stud. There is little or no pressure at the tip end of the stud 21, inasmuch as the main diameter oftheball is considerably further into the recess than this point. Furthermore, since the base 23 of the recess is usually a considerable distance within the bores l5, It at the wall, there is then appreciably less than the maximum pressure at the base 29-01 the stud against the outer edge of the wall. This gradient of binding or locking pressure of the stud against the wall is illustrated graphically for a rail head bond in Fig. 5a, and contributes greatly to the efiicient bonding and holding effect of my bond, yet limiting to a safe degree the stresses in the stud at the vulnerable line ofthe face of the rail 29, while at the same time effecting an efficient seal against seepage into the bore. and providing a. good electrical connection of the bond to the wall. In Fig. 5a the ordinate is scaled in accordance with distances along the stud, and points on the ordinate scale are transferred directly across from corresponding points of. the stud, in Fig. 5. The abscissas represent units of pressure of. the stud against the bore in the, rail head. As will be seen from the curve, the maxi- 6 I mumbmding pressure, occurs. at region 3.6.,which is, the region of maximum diameter of the ball: The region of high pressure extends inwardly as. far as region 34 of the stud which is approximately the original place of maximum diameter at the bore before the ball started to move inwardly into the recess. Owing to the flow of stresses, the high pressure region continues for a distance toward the base of the stud, approximately to the point 35', at about the base of the seating ball. From. this point the pressure; drops off quite rapidly as at '44? where contact orthe with the stud ends. At the. extreme tip 21,;the-

the physical properties of the stud or the length of the recess therein. In another instanceya small ball, for example, necessitates a relatively thicker wallof the stud at the tip and with a shall'cw recess the main solid body of the stud would be comparatively long, Such a design would produce, a moderate wall pressure at 36 while the upsetting action on the stud would expand it at the entrance into the bore, say 29, which would tend to. block ofi further upsetting inwardly to ward the relatively distant bottomof the recess 28, thus giving a maximum of wall pressure at the point of entrance of the stud in the bore. Such a design would be required to insure the utmost in sealing of the bore against seepage of corrosive brine, acids or gases.

Fig. 9 shows a modification of the stud con struction adapted for use with shallower devices than rail heads, for example with metal plates of limited thickness. In this figure, the stud 31' is shorter with respect to its diameter than is the stud in Figs. 1 to 8'; and it is proportioned this way in Fig. 9 to accommodate itself to the rather shallow, flat piece of metal 38, into which it: is inserted. Apart from the change in proportion, the construction is similar tothat in Figs. 1 to 7 and involves the use of the ball 3.0 inserted in the recess 26 of the studand. fittedagainst the cupped base of the bore.

Figs. 10, ll and 12 illustrate a desired arrangement ofthe railbond- 46 with the serpentine form of cables 41 shown in Fig. 7. It is preferable that the bends of the cable shall lie substantially within the region bounded by the line C-C of Fig. 12; as by confining the cable it is less subject to damage from dragging equipment or being caught by devices or the like.

Fig. 13- illustratesthe manner in which the successive blows of the hammer on the head 51! cause theball 5| to enter the recess 52-; and Fig. 13aillustrates the pressures under the successive blows. Fig. 13 is a section taken at line [3-43 of Fig. 11.

During the initial blow or blows the recess contour in contact with the ball is successively a surface parallel with the outer surface of the stud, as indicated by the periphery through which the line X is tendered; then the tangent becomes a surface of an angul-arity to the outer surface of the studs and slanted inwardly at a moderate angle Y; and with further blows the tangent increases to an increased angularity'z at'a more m an inward portion of the recess. By reason of the approach of the ball to the more restricted part of the recess in the stud, resistance to movement is increased as the end of the stud approaches the bottom of the recess into which it is being driven. During these successive blows the pressure variance changes according to Fig. 13a; that is during the initial blow or blows the pressure is represented by curve 12 and then increases successively by a second blow as represented by s, and by a third blow, t, and the final blow as represented by the curve f.

Fig. 14 is a modification in accordance with my invention in which the insert 54 instead of being in the spherical ball shape, shown in Fig. 13, is of a spheroid, comprising a spherical shaped outer end, a region of conical taper, and then an inner spherical end of lesser diameter than the outer spherical shape. The conical region and the wider region of the outer end are closely and intimately contacted with a corresponding spherical and tapered recess 55 in the stud of terminal 56. This tapered recess being carried inwardly within the stud to provide a channel of diminishing circular cross-section for the conical part of the insert and so as to maintain contact through the conical parts. This form of insert is useful in cases where it is desirable to produce at the outer end of the insert a greater rate of expansion of the stud than at the inner end. This is illustrated in conjunction with Fig. 14a, wherein D represents the large diameter and d represents the small diameter. The degree of area enlargement A is proportional, in any given unit length L, to D at the outer end; and thus at the smaller end the degree of area enlargement a is proportional in the same given unit length L, to 1 Since D is greater than d, and since the squares of these diameters are the measure of area changes due to the expansion from wedging, it follows that at the widest part of the insert the stud will be expanded the greatest. Curve M in Fig. 14a shows the relative degree of expansion at different distances Fig. illustrates a modification of ovoid shaped insert of Fig. 14, wherein the conical portion of the insert 58 engages the outer end of the recess 59 of the stud of terminal 60 and recedes from the wall of the recess toward the inner portion. Accordingly, when the head of this stud is hammered the outer end of the stud will begin to expand appreciably before the inner end, and accordingly the expanding action will occur at the outer end before, and to a greater extent, than at the inner end. This modification may have important application, for example, where soft metals are involved, such as aluminum or copper for the stud, hard brass, stainless steel, or the like for the insert. With the use of such materials the conformations of Fig. 15 may be desirable to insure the fullest amount of expansion of studs with the earliest application of pressure, or with comparatively light blows on the terminal head. In making connection by such a means between a conductor and an electrode, for example in cathodic protection of buried pipelines, where soft metals such as aluminum, magnesium and zinc are used for the electrodes, such as modification as shown in .Fig. 15 would have particular advantages, since from the anode would be minimized, and a soft stud of poor mechanical characteristics would tend to deform starting as it would at the bottom of the hole in the body being connected. Such an elongated insert would be an advantage over the spherical insert mainly in that it would, upon completion of the driving, bear on practically its full length against the wall of the stud, thereby reinforcing it structurally and developing a pressure outwardly for dependable electrical contact.

Fig. 16 illustrates another modification of a non-spherical type of insert involving some nonconformities of the respective tapers of the insert 62 and of the recess 63. In Fig. 16 the difference in tapers is opposite from that of Fig. 15 in that in Fig. 16, the point of contact of the insert against the conical wall of the recess is toward the inner end and there is no substantial contact at the outer end of the insert except where it is held by the crimping over of the outer end of the stud of terminal 64. In this modification the first region of exapansion of the stud is near the inner end where the small end of the tapered decess is located. This part expands first followed progressively by expansion at the outer end. This may be useful in specialized cases, for example, where the bottom of the hole or bore, for example in the web of a rail, is of questionable thickness, and consequently calls for an early start in the expansion as the entering part of the stud in such a rail web. By a proper degree of respective curvatures of either one or both of the surfaces of the insert or recess, it is apparent that a closer proximation of uniform pressure of the stud against the enclosing hole can be achieved when the amount of movement, or driving of the terminal is predetermined. This modification, has in effect, a pressure characteristic opposite to that described in respect to Figs. 14 and 15. In Figs. 1 to 16 furthermore, the principle involving the fiow of said material and its elastic expansion in passing the maximum diameter does not come into play until the driving eliminates the void between the respective areas of the recessed wall and of the insert.

Fig. 17 shows a modification comprising an ovoid or egg shaped insert 66 in an ovoid recess El of the stud of terminal 68. Its functioning is similar, although not necessarily identical with the modification shown in Fig. 14. The particular curvatures govern the degree of expansion at all degrees of driving action, and consequently the degree of pressure on the enclosure of the stud.

Fig. 18 shows a modified form of the shape of the insert 10 and recess H conformation shown in Fig. 17, with both ends of the spheroid being of the same radius of curvature. The use of this form has some advantage in avoiding the possibility in assembly of carelessness in insertin the egg shaped insert wrong end foremost into the recess.

Fig. 19 is another modification showing an ovoid or egg shaped insert 12 in a recess 13 having the shape which is the combination of a curve and a straight wall angularity, and a concave wall configuration.

Fig. 20 shows a modification similar to that shown in Fig. 13 in that there is shown a bore 15 in the rail 16 of a standard form as established by the Association of American Railroads, and in which there is installed a stud 1'! containing a recess 18 of the type'shown in Fig. 19

same general type shown in Fig. 14, but to which .has been appended on its lower or outermost end an auxiliary extension 80 adapted to permit engagement with the bottom of the bore in the rail at a distance predetermined by the length of this extension Or protrusion. It is shown in the form of a .neck to fitin the angularity in the bottom of the bore which is ordinarily drilled with a bit with a cutting edge ground to provide an enclosing angularity of 135, that is an angularity of 6'7 /2 with the axis of the bit. Such an extension to the insert would readily provide a firm base for stopping the insert movement and driving, particularly in cases where the driving is being done against the bottom of holes in the softer metals. In Figs. 17, 18 and 19, radii R, R, R" and R"indicate variations in extent, required to achieve the desired curvatures.

It will be understood that the several modifications thus described do not exhaust all possible modifications of the sphere and ovoid shapes, but are illustrative of some of the possible combinations and conformations within fields and applications. It is characteristic of the group of modifications that they are featured by the placing of the insert, whether it be a sphere, a sphereoid,

an ovoid, or a cone within a recess so fashioned and so conformed that they function cooperatively on driving, to permit flow or deformation of metal over and around the front of the insert, the insert remaining stationary by abutting on the bottom of the hole in the receiving body. It may not always be required that a bottomed hole be used into which the stud with its insert is driven. For example, it is possible even with a bore or hole without a bottom, such as where a hole runs completely through the web of a rail, to use the stud of my invention. This may be done simply by providing an auxiliary backing tool within or at the side of the hole opposite from that into which the stud is being driven and against which the insert may be forced to provide its desired upsetting action on the stud. This backing tool can at the same time be made to swage over the end of the stud more effectually as needed.

It will be apparent from the foregoing several modifications that I provide a choice of contour of the insert and of the walls of the recess which may be formed in funnel shape or inverse cone in curvatures to meet specific needs, as for instance by restrictions regarding wall strength at various points, or combinations of these shapes. It is aso quite practical, as the application of these curvatures of both insert and recess materials may dictate, to place annular rings or grooves or convolutions about the insert while within the recesses, or both, to enhance by multiplication the anchoring and holding power of the insert in the recess. A single such annular groove ring 82 is shown in Fig. 20.

As high electrical conductance is usually desired in such bonds or connectors, the foregoing descriptions have referred to metals. It should be understood however, that other materials than metals might be used for particular applications. For instance, a plastic such as rubber, neoprene, or some such material having mixed with it a suitable amount of conducting material, such as carbon black forming a so-called semi-conducting rubber, might be used in certain applications. Such compositions are frequently free from deterioration or corrosion to which metals may be subject.

By my invention I have provided a connector adapted for use in many situations and especially suited for use as a railbond. My connector is characterized by the simplicity of its application and the ease and dependability of its installation with so-called untrained labor, coupled with its essential durability and permanence and good electrical connection. By reason of the arrangement of th insert held in its socket or recess .by the crimped over tip of the stud the connector can be carried around without loss of the insert.

By reason of the conical or curved tapering or cupping of the base of the bore in the member to be connected, in cooperation with the insert in the socket, the connector is self centering, that is, a rounded or spherical portion of the insert protruding from the stud automatically centers into the bore. This feature substantially reduces or eliminates the tendency of mis-alignment of the study in the hole, that is avoids the tendency of cocking over through faulty driving, which has heretofore been experienced in the use of prior known connecting devices. Furthermore the permanence or holding capacity of my stud connector is greater than that heretofore experienced in the use of stud connectors. This greater holding eifect is due to the progressive upsetting of the metal of the stud as the insert is forced into the recess, over a substantially large area at the circumference of the stud, coupled with the fact that this binding or high pressure area develops from near the tip of the stud rather than from near the base-(in those modifications where the configurations produce the greatest binding pressure at the stud tip). By reason of this form of pressure gradient, the pounding of heavy locomotives and cars on railroad tracks has less effect on loosening my stud than is the case with prior known connectors; and furthermore, owing to the lack of excessive binding pressure at the base of the stud, that is, at the entering point in the rail, as well as the full, unimpaired metallic cross sectional area of the stud there, the vibration and shocks cannot normally break off the stud of this region.

Moreover, by reason of my construction, comprisin the above-noted type of gripping action there is not as much tendency nor need, usually, for the stud to upset or deform at its base, as in the use of the other types of connectors. Such excessive upsetting near the base of the stud is an extreme disadvantage as it would tend to resist further driving in of the stud near its end and thereby reduce the desired holding effect near the tip of the stud. Moreover, being of solid metal at the line of the face of the rail, and being so resistant to excessive upsetting in consequence, in this region, as compared with stud areas opposite the recess, my stud has a most desirable resistance to actual destructive bulging under the terminal head and before entering the bore in the rail, the sharp edge of which bore, producing in bulging bond studs, a recognized incipient point of fracture. Recourse to a re.- moval of this sharp entering edge of the bore has been a costly practice that is not necessary in my bond. The progressive increase of the gripping area from near the tip toward the base has a further advantage of squeezing out from the bore hole of any undesirable moisture or other foreign matter which might be condensed or introduced into the hole, thereby minimizin the presence of substances which might otherwise .tend to produce high resistance or corrosion in the connection.

My connection maintains throughout a long period of its life a high degree of electrical conductivity inasmuch as the insert is always maintained in firm contact with the cup of the bore, while at the same time the metal of the stud is firmly bound against the wall of the bore over a wide area.

'My novel bond construction is furthermore especially well suited for extraction from a rail or other location by simple extracting means without breaking off and leaving the broken stud in the rail, as frequently is the case with other bonds. This results from the fact that the minimum stud cross sectional area and the maximum holding power is toward the tip end of the stud rather than the base end. In consequence, when a pulling or extracting force is applied between the rail head and the head of the stud, thestud initially tends to neck down somewhat at its base at 29, and this necking down and localized loss of holding power tends to continue progressively toward the tip end of the stud until the stud is finally freed without breaking. Furthermore, distortion of the stud is thereby minimized and the bond is left uninjured for subsequent usage, if desired.

The tendency toward loosening or actually falling out from the rail head of prior known types of connectors has been due to a lack of sufiicient gripping or holding power, in the case of studs which through carelessness can be easily underdriven; while in the case of those prior known kinds of connectors in which the studs can be overdriven, the studs have often actually forced themselves out by reason of the excessive pressure from their own overdriven internally flowable elements. By reason of my stud construction, however, this danger of loosening and fallin out is greatly reduced or completely eliminated by reason of the stable, virtually incompressible and distortion-resistant insert embedded in a tough shell of the stud which is only somewhat less hard than the insert. M design encompasses two distinct means of expansion of the stud; one agency is the expansion by means of the wedging of the insert, localized near the tip of the stud,,and the other is the upsettin of the stud itself, this upsetting being subsequent to the wedging by the insert and carried on progressively and controlled by the contour of the recess to any required degree in the successive changes in cross-sectional area of the stud.

It will be observed that while I show in Fig. 16 a flattened surface on the inner or narrow end of my insert 62, and a conical end similarly in Fig. 20, and rounded ends likewise in my remaining illustrations of inserts, these surfaces in all cases have no function in the operation of the insert and these illustrative surfaces, amongst others not shown, are interchangeable in the various combinations of recess and insert contours.

It will be recognized from the foregoing description and statement of advantages that my connectors are useful in many applications, and are not necessarily limited to railbonds or the particular applications mentioned. Furthermore, it will be apparent that it is not necessary to put connecting studs on both ends of the cable, as in some cases it may be desirable, or required, only to put the stud on one end for connection with an electrical member, while attaching the other end of the cable to a position or '12 terminal in some other manner, for example, soldering or welding.

Iclaim:

1. An electrical terminal adapted to be anchored within a bore in a member to be connected to the terminal, comprising a head adapted to be driven, a stud protruding from the head and adapted to be inserted within the bore, said stud having a centrally located recess in its outer end, an insert of harder material than the stud mounted within the recess and having a spherical-shaped outer end protruding beyond the end of the stud in the unexpanded condition of the stud, the outer portion of the recess being in the form of a socket embracing a portion of said spherical-shaped outer end to anchor the same within the recess in a position in which the inner end of the insert lies in spaced relation to the bottom of the recess, the walls of said recess in the unexpanded condition of the stud having circular cross-section areas which diminish in size progressively from a point corresponding substantially to the diameter of said sphericalshaped outer end in the direction of the inner end of the stud to a point spaced inwardly of said insert, whereby as the insert is driven into the recess it will exert a progressively increasing degree of lateral pressure as the insert moves toward the base of the recess and the insert will be locked within the recess in any position thereof.

2. An electrical terminal adapted to be anchored within a bore in a member to be connected to the terminal, comprising a head adapted to be driven, a stud protruding from the head and adapted to be inserted within the bore, said stud having a centrally located recess in its outer end, an insert of harder material than the stud mounted within the recess and having a spherical-shaped outer end protruding beyond the end of the stud in the unexpanded condition of the stud, the outer portion of the recess being in the form of a socket embracing a portion of said spherical-shaped outer end to anchor the same within the recess in a position in which the inner end of the insert lies in spaced relation to the bottom of the recess, the walls of said recess in the unexpanded condition of the stud having circular cross-section areas which diminish in size progressively and uninterruptedly from approximately the diameter of said spherically shaped outer end to a point spaced inwardly of said insert thereby to provide for inward movement of the insert within the recess as said head is driven and progressively increasing lateral pressure exerted by the insert along said walls.

3. An electrical terminal adapted to be anchored within a bore in a member to be connected to the terminal, comprising a head adapted to be driven, a stud protruding from the head and adapted to be inserted within the bore, said stud having a centrally located recess in its outer end, an insert of harder material than the stud mounted within the recess and having a spherical-shaped outer end of relatively large diameter protruding beyond the end of the stud in the unexpanded condition of the stud and a sphericalshaped inner end of smaller diameter than said outer end, the outer portion of the recess being in the form of a socket embracing a portion of said spherical-shaped outer end to anchor the same within the recess in a position in which the inner end of the insert lies in spaced relation to the bottom of the recess, the walls of said recess in the unexpanded condition of the stud having circular cross-section areas which diminish in size progressively from a point corresponding substantially to the diameter of said sphericalshaped outer end in the direction of the inner end of the stud to a point spaced inwardly of said insert, whereby as the insert is driven into the recess it will exert a progressively increasing degree of lateral pressure as the insert moves toward the base of the recess and the insert will be locked within the recess in any position thereof.

4. An electrical terminal adapted to be an chored within a bore in a member to be connected to the terminal, comprising a, head adapted to be driven, a stud protruding from the head and adapted to be inserted within the bore, said stud having a centrally located recess in its outer end, an insert of harder material than the stud mounted within the recess and having a spherical-shaped outer end of relatively large diameter protruding beyond the end of the stud in the un expanded condition of the stud and a sphericalshaped inner end of smaller diameter than said outer end, the outer portion of the recess being in the form of a socket embracing a portion of said spherical-shaped outer end to anchor the same within the recess in a position in which the inner end of the insert lies in spaced relation to the bottom of the recess, the walls of said recess in the unexpanded condition of the stud having circular cross-section areas which dimin ish in size progressively and uninterruptedly from approximately the diameter of said spherically shaped outer end to a point spaced inwardly of said insert thereby to provide for inward movement of the insert within the recess as said head is driven and progressively increasing lateral pressure exerted by the insert along said walls, the outer sides of said insert intermediate said spherical-shaped ends conforming substantially to the portion of the walls of said recess of diminishing cross-section areas.

5. An electrical terminal adapted to be anchored within a bore in a member to be connected to the terminal, comprising a head adapted to be driven, a stud protruding from the head and adapted to be inserted within the bore, said stud having a centrally located recess in its outer end, an insert of harder material than the stud mounted within the recess and having a spherical-shaped outer end protruding beyond the end of the stud in the unexpanded condition of the stud, the outer end of the stud having a lip portion embracing said insert outwardly of the diameter of said spherical-shaped outer end to anchor the insert within the recess in a position in which the inner end of the insert lies in spaced relation to the bottom of the recess, the walls of said recess in the unexpanded condition of the stud having circular cross-section areas which diminish in size progressively from approximately said diameter of the sphericalshaped outer end thereby to provide for progressively increasing lateral pressure exerted by the insert along the walls of the recess as the insert is forced inwardly toward the bottom of the recess.

6. An electrical terminal adapted to be anchored within a bore in a member to be connected to the terminal, comprising a head adapted to be driven, a stud protruding from the head and adapted to be inserted within the bore, said stud having a centrally located recess in its outer end, an insert of harder material than the stud mounted within the recess and having a spherical-shaped outer end protruding beyond the end of the stud in the unexpanded condition of the stud, the outer end of the stud having a lip portion embracing said insert outwardly of the diameter of said spherical-shaped outer end to anchor the insert within the recess in a, position in which the inner end of the insert lies in spaced relation to the bottom of the recess, the inner end of said insert being of spherical shape and the sides of the insert intermediate the ends thereof substantially conforming to the adjacent wall portions of the recess, the walls of said recess in the unexpanded condition of the stud having circular cross-section areas which diminish in size progressively from approximately said diameter or the spherical-shaped outer end thereby to provide for progressively increasing lateral pressure exerted by the insert along the walls of the recess as the insert is forced inwardly toward the bottom of the recess.

7. An electrical terminal adapted to be anchored within a bore in a member to be connected to the terminal, comprising a head adapted to be driven, a stud protruding from the head and adapted to be inserted within the bore, said stud having a centrally located recess in its outer end, an insert of harder material than the stud mounted within the recess and having a spherical-shaped outer end protruding beyond the end of the stud in the unexpanded condition of the stud, the outer end of the stud having a lip portion embracing said insert outwardly of the diameter of said spherical-shaped outer end to anchor the insert within the recess in a position in which the inner end of the insert lies in spaced relation to the bottom of the recess, the inner end of said insert being of spherical shape having less diameter than the outer end and the sides of the insert between said ends providing a region of conical taper, the walls of said recess in the unexpanded condition of the stud having circular cross-section areas which diminish in size progressively from approximately said diameter of the spherical-shaped outer end thereby to provide for progressively increasing lateral pressure exerted by the insert along the walls of the recess as the insert is forced inwardly toward the bottom of the recess.

8. An electrical terminal according to claim 1 in which the insert is generally ovoid in shape and the recess in the stud is at least in part generally ovoid in shape.

IRVING W. EDWARDS.

REFERENCES CITED The following references are of record in the of this patent:

UNITED STATES PATENTS Number Name Date 751,902 Dodge Feb, 9, 1904 856,127 Brennan June 4, 1907 1,938,563 Deems Dec. 5, 1933 2,074,379 'Everett Mar. 23, 1937 2,181,467 Stolnacke et a1 Nov. 28, 1939 2,314,737 Sabol Mar. 23, 1943' 

